Current Products and Practice Nickel allergy and orthodontics

Index words: Delayed hypersensitivity, nickel allergy, nickeltitanium, nickel-free Address for correspondence: Gerry Rahilly, Orthodontic Department, Leeds Dental Institute, Clarendon Way, Leeds LS2 9LU, UK. Email: [email protected] 172 G. Rahilly and N. Price Features Section JO March 2003 increased by mechanical irritation, skin maceration, or oral mucosal injury, all of which may occur in orthodontic treatment. Environmental temperatures and duration of exposure may also be factors. The lesions of contact stomatitis may be variable and may be barely visible. Itching is not a common feature of contact stomatitis (see Table 1)8 and extra-oral reactions are more common than intra-oral reactions. Diagnosis of nickel allergy It is important to make a correct diagnosis of nickel allergy, symptoms of which may occur either within or remote to the oral environment. The following patient history would suggest a diagnosis of nickel allergy: • previous allergic response after wearing earrings or a metal watchstrap; • appearance of allergy symptoms shortly after the initial insertion of orthodontic components containing nickel; • confined extra-oral rash adjacent to headgear studs. A dermatologist should confirm the diagnosis by patch testing using 5 per cent nickel sulphate in petroleum jelly. Lesions due to other causes should be eliminated: • candidiasis; • herpetic stomatitis; • ulcers due to mechanical irritation; • allergies to other materials such as acrylic. All adverse reactions to any orthodontic material should be reported on an ‘Adverse Reaction to Dental Materials’ reporting form obtainable from Adverse Reaction Reporting Project, Centre for Biomaterials and Tissue Engineering, Department of Restorative Dentistry, University of Sheffield, Sheffield S10 2TA, UK. Alternative materials for nickel allergy patients The potential for orthodontic metals to cause allergic reactions is related to the pattern and mode of corrosion, with subsequent release of metal ions, such as nickel, into the oral cavity. This is dependent not only on the composition of the metal, but also the temperature, pH of the environment, and wear of the wire due to friction from sliding mechanics, abrasion, presence of solder, and strain of the wire.9 Stainless steel contains 8 per cent nickel, whilst nickel-titanium wires may contain in excess of 50 per cent.